This application relates to bone fixation and fusion systems, for example for the fusing together of toe bones or the like, by firmly locking them in abutting relation to permit good healing. This is accomplished through the use of male and female connectors, each of which, when bone fusion or fixation is the desired result, has external bone threads so that each of the connectors may be driven into a separate piece of bone or opposing ends of the same bone, as at a fracture.
The male connector is a solid body having a slotted boss with external threads adjacent to a distal end. The female connector defines an internally threaded bore in which the boss of the male connector may be threadedly engaged in a somewhat resilient, spring-like manner resulting from the cross cut slots, for retention of the two connectors together.
This threaded interconnection permits the connectors to be engaged in a well-fitting, solid connection which nevertheless is highly adjustable in its length by adjusting the depth to which one connector is inserted into the other. However, the threaded interconnection may also permit one connector to rotate with respect to the other after installation, which may be undesirable or harmful. Also, the shape of the threads of the threaded interconnection, together with the flexibility of the slotted boss, may permit a camming action which could result in the connectors being axially pulled apart if sufficient force is applied.
By this invention, a bone connector system is provided which comprises first and second connector members. At least one of the connector members carries an external bone screw thread to permit securance within a bone. In the circumstance where two bones or two parts of a bone are being connected together for fusing or the like, both of the connectors may carry external bone screw threads, to permit their separate securance within separate bone parts. Otherwise, one of the connector members may connect to an artificial tooth or another attachment to a bone.
One of the connector members defines a projection or boss having a distal or outer end. One or more longitudinal slots extend through the boss adjacent to its outer end. The boss also carries a plurality of loops or convolutions of an external screw thread adjacent to the outer end. The other of the connector members defines a bore for receiving the boss, and having a plurality of loops or convolutions of an internal screw thread which is proportioned to engage the external thread of the boss when the connectors are brought together. The internal screw thread and the external screw thread may fit together with a multiple-loop, close, tight fit without any mispositioning. The screw threads have differently-sloped flanks, one inclined at a small acute angle and one at a large acute angle to the longitudinal axis of the connector, so that it is much more difficult to axially pull the connectors apart than it is to push them together.
The outer surface of the boss has a portion of non-circular peripheral shape disposed for mating engagement in a portion of the bore having a similar non-circular peripheral shape when the boss is disposed in the bone, to prevent relative rotation of the connector members.
If desired, one or both connector members may define a central lumen, to permit a guidewire to extend through either or both connector members to facilitate placement thereof at a desired position in a bone.
FIG. 1 is a perspective view showing the two separate connector members of the bone connector system of the invention;
FIG. 2 is an enlarged sectional view, taken generally along line 2xe2x80x942 of FIG. 1, of one of the connector members;
FIG. 3 is an enlarged, fragmentary view in partial longitudinal section of the bone connector system of FIG. 1, shown in a position of implantation within and connecting two bones;
FIG. 4 is a perspective view similar to FIG. 1 of a modified bone connector system; and
FIG. 5 is a fragmentary view in partial section similar to FIG. 3, illustrating another embodiment of the bone connector system.